Well I don't know exactly what the wiring harness does but to answer your other two questions:
VVT is variable valve timing - just like the v-tec that the honda boys have.
The problem with the 6-speed is that the gears are thinner than in the 5-speed in order for them all to fit into the housing and since they are thinner they are prone to breaking; especially with the way someone with a S15 motor or car would drive that thing. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=';)'> Hope this helps some.
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